Silage and other perishable materials are frequently stored in air-tight storage structures or silos. As there can be a substantial differential in pressure between the atmosphere and the sealed interior of the structure, a breathing system is normally used with the sealed structures. One commonly used type of breathing system is a closed breather bag, which is suspended in the upper end of the structure and is connected via a tube in the roof of the structure to the atmosphere. The bag will expand and contract in accordance with pressure variations between the interior and exterior of the structure. The breather bag has the advantage that it can be readily removed through an opening in the roof for repair or replacement, but the breathing capacity of this type of system is, of course, limited to the volume of the breather bag.
Breather systens utilizing a diaphragm have also been suggested in the past, such as those shown in the patents to Martin U.S. Pat. No. 2,551,217 and Bahlen U.S. Pat. No. 3,076,403. While a diaphragm type breather system can increase the breathing capacity over a breather bag, repair or replacement of the diaphragm has been a problem that has not been successfully solved. To repair or replace the diaphragm in the prior art systems, it has been necessary for a workman to enter the sealed structure using a respiratory system and to erect a scaffold on the stored material up to the level of the diaphragm. Due to the difficulties in maintenance of the diaphragm, diaphragm-type breather systems have not been successfully utilized in the field.